allows nested lists.

correct_way.py

def sv_main(vc=[], vf=[]):

    in_sockets = [
        ['v', 'vc', vc],
        ['v', 'vf', vf]]

    edges_out = []
    verts_out = []
    
    for idx, vz in enumerate(vf[0]):
        b = []
        b.append(vz)
        b.extend(vc[idx])
        verts_out.append(b)
        edges_out.append([(0,n+1) for n in range(len(b)-1)])
        
    # out boilerplate
    out_sockets = [
        ['v', 'Vecs', verts_out],
        ['s', 'Edges', edges_out]
    ]

    return in_sockets, out_sockets